Britain is "sleepwalking" into a crisis in which people's homes, businesses and livelihoods will be destroyed by more extreme weather events, Ed Miliband has warned.

The Labour leader said "the science is clear" that climate change is to blame for floods that have swept across the country - and will lead to more such events.

Yet political divisions mean the country is failing to act and instead heading into a "national security crisis", he added.

Image:Mr Miliband during a visit to flood-hit Wraysbury

In an interview with the Observer newspaper, Mr Miliband argued: "Storms and severe weather conditions that we have might have expected to occur once in 100 years, say, in the past, may now be happening more frequently and the reason is ... that the climate is changing."

The second wettest winter in 2012 and this winter's one in 250-year event led him to one conclusion, he added.

"If you keep throwing the dice and you keep getting sixes then the dice are loaded. Something is going on."

Conservative Defence Secretary Philip Hammond, who has admitted the military could have been brought in earlier to help deal with the flooding crisis, said Mr Miliband had not said "anything new".

He said: "Climate change is clearly happening, it is clearly a factor in the weather patterns that we are seeing.

Video:Helicopter Tour Of Flooded Britain

"That's why we are investing significant amounts of money in increasing our flood resilience in the UK.

"Of course these floods are a terrible tragedy for all the people affected, but we shouldn't forget that hundreds of thousands of properties have been protected from flooding by the investment we've made over recent years."

Mr Miliband insisted he was not trying to score political points.

Video:Floods Misery Continues For Many

But his words will be interpreted as an attack on the Prime Minister, who has been less passionate about his environmental views in recent years.

David Cameron once called on the electorate to "vote blue, go green".

But he has faced growing scepticism in his own party and recently promised to row back on green levies on energy bills in the face of public anger.

Video:Sky News UK Weather Forecast

Mr Cameron has also faced calls from his own Chancellor, George Osborne, to make sure the green agenda is held behind the economic one, particularly in times of austerity.

But it could be the party is facing a shift of attitudes among the public.

The Observer has also run an Opinium poll showing that more than half of voters - 51% - believe the recent floods are a sign of climate change and global warming. That is more than double the 24% who do not, and the 20% who are neutral.

It comes as Boris Johnson, the Tory Mayor of London, blamed the "vast and malignant rage of mother nature" for the floods.

In an article in the Sun on Sunday, he contrasted the disaster to another problem he describes as "entirely avoidable" - the recent Tube strike in London.

"There are natural disasters, and man-made disasters," he said.

Video:Clean-Up After Deadly UK Storm

A Department of Energy and Climate Change (DECC) spokeswoman said: "The scientific evidence behind climate change is clear. Britain has adopted some of the most ambitious climate change targets in the world to tackle the threat."

She added: "The Government is planning for the impacts of extreme weather and will continue to do all it can.

"We are spending £2.4bn on flood management and protection from coastal erosion over four years. That is more than ever before."